This invention relates to insulated cables and, in particular, to the use of shielding tape incorporating microencapsulated lubricant. In various types of cable, it is necessary to employ a layer of shielding tape surrounding the conductors. The purpose of this shielding tape is to reduce the chance of extraneous external signals effecting data carried by the cabling. The shielding tape may be applied to the cable by wrapping it in a spiral manner or by wrapping it around in a sleeve-like fashion by pulling it through the die simultaneously with pulling the cable through a die. However, the shielding tape is usually a thin layer of foil sometimes bonded to a plastic substrate and the thin layer of foil often becomes scuffed or torn during the manufacturing process when rubbed against machine and cable parts. To prevent this, prior art has applied a thin layer of lubricant to the tape during manufacturing.
Prior art attempts to apply lubricating oil in a tape manufacturing process have or had only limited success. For example, the two methods currently used are to apply oil by the drip method or using a prelubricated sponge. Using either of these methods, the amount of oil can only be roughly controlled. Too little oil and the tape becomes torn or scuffed, therefore, not performing in a satisfactory manner; or, too much oil and the oil is soaked up by the plastic substrate which changes its dielectric characteristics and, therefore, changes the characteristics of the cable. Also, if too much oil is applied, it adds to the cost of the cable unnecessarily. Excess oil can also create processing problems. Attempting to extrude a plastic jacket over excess oil results in blistering or bubbling of the plastic. Prelubricating tape prevents these problems.